The way in which the kidneys regulate sodium balance, water balance, glomerular filtration rate and renal growth over a wide range of renal function is largely unknown. Renal prostaglandins are one of the many factors which have been implicated in controlling these many aspects of renal function. Of the many hormones capable of modulating renal function, prostaglandins would appear to be uniquely capable of varying numerous renal functional parameters because of their site of production both in the cortex and the medulla. The objective of this study is to clarify the role of renal prostaglandin synthesis and release on these numerous aspects of renal function by studying conscious animals and by using a very sensitive membrane receptor assay for prostaglandin E. Rats, rabbits and dogs will be studied. The knowledge obtained from these studies should help to better understand more of the basic mechanisms involved in the control of renal function both in normal and pathologic states.